Method of treating mill-scale.



' srarns PATENT enrich.

smnm x m. IBECKET, or NIAGARA FALLS, NEW YORK, ASSIGNQR TO ELECTED mnramnunorcn. comrAiry, or NIAGAnA FALLS, NEW YORK, A CORPORATION or WEST VIRGINIA.

METHOD OF TREATING MILL-SCALE.

No Drawing.

To all whom it may concern:

Be it known that I, Fnnonmox M. Bnoxnr, a subject of the King of Great Britain, residing at Niagara Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Methods of Treating Mill-Scale, of which the following is a specification.

In my prior Patents Numbers 1,081,566 and 1,081,570, patented December 16, 1913, I have described certain'processes applicable to the treatment of ores, concentrates, or like products, of the iron-tungstate type, to obtain therefrom tungsten or its alloys in which the ratio of tungsten to phorphorus,

expressed as g, is materially-higher than in the unreduced material.

The present invention relates to the application of processes of this kind to the oxidized material known as high-speed mill-scale. This scale is produced in considerable quantities as a by-product in the manufacture of high-speed steel, and consists, essentially, of oxid compounds of iron and tungsten, usually with smaller proportions of chromium and vanadium, and containing also considerable quantities of cobalt when derived from the so-called cobalt steels. The metals are present in the scale in the form of oxid, but are not, in all cases at least, in their highest state of oxidation.

The following is the composition of a typical high-speed mill-scale:-

Iron 57.66 per cent. Tungsten 12.25 Chromium 3.23 Vanadium 0.43 Manganese 0.47 Silicon 4 0.75 Carbon 0.35

Phosphorus 0.015 to 0.030

Specification of Letters Patent.

Application!!! April 8, 1914. Serial No. 830,417.

Patented Feb. 2, 1915.

tamed therefrom by known processes of silicon reduction, are as follows The alloy so obtained is utilizable as such, or, with appropriate additions, it is available for the manufacture of steels of modified composition. I have found, however that such high-speed mill-scales usually contain a proportion of phosphorus which is distinctly objectionable. Moreover, the product of direct reduction of the scale is comparatively low in tungsten: this of course necessitates the use of a relatively large proportion of the alloy in compounding a given steel, from Which it results that the phosphorus-content of the-steel is not much less than that of the alloy. These difficulties are avoided by treating a mill-scale, before reduction, with an acid reagent which serves the double purpose of removing iron, and thereby concentrating the tungstencontent, and of removing phosphorus, and

I have found that these mill-scales yield a large proportion of their iron, together with substantially all of their phosphorus, to acids, such as sulfuric acid, even in the cold. In other words, the very high temperature to which they have been subjected in the course of their production has not resulted, as might be expected, in converting the iron into such an 1nsoluble condition as occurs when iron-tungstate ores are ignited or calcined.

Illustrative conditions for the acid-treatment are as follows: The scale is ground to pass an eight-mesh screen and introduced into a bath of sulfuric acid of 1.2 to 1.4 specific gravity. It is then digested for some hours, preferably with agitation. The action proceeds at normal temperature, or more rapidly at 70 C. Higher temperatures may be used but involve increased losses of tungsten. The quantity of acid should preferably be sufficient to combine with the total iron-content of the ore,'and may be in considerable excess of this prothereby increasing the ratio portion. Following this digestion, the resi-' ing such excess as would yield a reduced product undesirably high in silicon. Lime or other flux may be added in-proportion to form with the silica a suitable slag, as is well understood in this art.- According to this method, up to 7 5 per cent. or somewhat more of the total iron-content of the millscale may be extracted without entailing material losses of tungsten, the loss of tungsten by solution being usually only a fraction of one per cent. of the tungsten-content. The alloys resulting from the reduction contain -45 per cent. of tungsten or more, according to'the amount of iron removed, and are, for practical purposes, free from phosphorus.

I claim 1. The herein-described method of preparing tungsten alloys from high-speed millscale contaming tungsten, which consists in 1 extracting a portion of the iron and thereby from, and reducing the resulting purified concentrate by means of a non-carbon reducing-agent.

3. The herein-described method of preparing tungsten alloys from high-speed millscale containing tungsten, which consists in concentrating the tungsten-content of the scale and removing phosphorus therefrom by an acid reagent, and reducing the resulta ing purified concentrate by means of, a noncarbon reducing-agent.

In testimony whereof I aflix my signature in presence of two witnesses.

FREDERICK M. BECKET.

G. C. FURNEss, 

